Wright Engineering have recently completed a project for Lafarge Aggregates who are a major supplier of innovative asphalts and concretes, as well as rock, sand and gravel, road surfacing solutions and waste management services.
The project at their Whitwell Quarry, Nottinghamshire site involved the design and installation of all the civil works including the installation of two new Rotex vibratory feeders and several major improvements to the existing conveyor system.
The objective of the project was to recycle a sand replacement material which is screened off and conveyed via conveyor to a Maglime Plant where it was processed into Maglime. Due to a seasonal demand, when the storage facility is full this product has to be dumped into the quarry using dumpers.
The original specification involved the installation of the two vibratory feeders under the screen under pan outlets to feed a conveyor which in turn transferred material onto a steep inclined conveyor. This conveyor incorporated a two-way chute facility which allowed material to be diverted into dump trucks if the crushing plant suffered a breakdown or stoppage.
This conveyor then fed material into a VSI type crusher which fed a steep inclined conveyor delivering material into a sizer. This screened the product and supplied material onto a steep conveyor which delivered the sized product onto the existing conveyor which fed the Maglime Plant. Any oversize product from the screen was delivered onto a further conveyor which discharged onto the conveyor in the system so the oversize could be re-circulated through the system for further sizing.
The crusher, screen and link conveyor were all housed in one common building.
Although the constraints of the site had dictated the original specification Wright Engineering were faced with the contentious issue of chevron belts conveying at various angles with all the potential performance and maintenance questions that arise.
Having been successfully awarded the contract Wright Engineering were asked to improve the plant layout to eliminate the use of any chevron belts. This was achieved by a complete redesign of the plant layout which involved utilising the site space to its maximum. The new redesigned plant now provides the original feed from the screen onto the conveyor which transfers onto a secondary feed conveyor which is now an inclined catenary troughed belt feeding the crusher.
This belt incorporates a plough on the horizontal section which allows the product to be diverted into dump trucks should the plant have a breakdown/stoppage.
The crusher feed conveyor then transfers onto the sizer feed conveyor. The product is then fed onto the screen feed conveyor which inclines up inside the existing screen house and transfers onto the existing conveyor which feeds the Maglime bunker. Any oversize product is fed onto a re-circulatory conveyor feeding oversize back through the crusher.
The Maglime Bunker has been completely refurbished and lined with perplas by Lafarge’s site engineers. The existing bottom section which fed the existing Maglime product to the Maglime store has been redesigned by Wright Engineering enabling it to feed either the existing Maglime circuit or the new concrete sand product conveyor with an actuated clamshell door.
This conveyor cantilevers outside the Maglime Bunker House allowing it to feed dump trucks which then deliver the product into a new storage shed.
The storage shed was also constructed by Wright Engineering and is of a steep pitch portal design with high concrete self-supporting retaining walls. The building is clad on three sides down to the top of the concrete walls and the front is open for access.
The redesign of the plant has now enabled the excess product to be resized and reshaped providing Lafarge with a product which can now be sold as concrete sand or Maglime.